Fuel injection valve

ABSTRACT

A fuel injection valve, especially an injection valve for fuel injection systems of internal combustion engines, includes a piezoelectric or magnetostrictive actuator and a valve-closure member, which can be actuated by an actuator via a valve needle and interacts with a valve-seat surface to form a sealing seat. An intermediate piece is connected via a first flexible seal to a support plate; the support plate is connected via a second flexible seal to a driver at the valve needle; and the driver is connected via a third flexible seal to the intermediate piece, thereby creating a sealed hydraulic translation device.

BACKGROUND INFORMATION

A fuel injection valve is described in German Patent Application No. DE195 00 706 A1.

The device for metering liquids and gases, described in German PatentApplication No. DE 195 00 706 A1, in particular in fuel injection valvesin internal combustion engines, has a hydraulic displacement amplifierfor converting the actuator travel of a piezoelectric actuator into anincreased stroke of a valve needle. To spatially integrate thedisplacement amplifier in the valve housing to give a small overallvolume, the lifting piston of the displacement amplifier is providedwith an end section that has a reduced diameter and projects into arecess in the working piston of the displacement amplifier. A diskspring lying in the amplifier chamber bordered by the pistons pressesthe working piston against the actuator, and a helical compressionspring arranged in the recess concentrically to the end section pressesthe lifting piston against the valve needle.

Influences from temperature changes, wear, and manufacturing toleranceson the actuator displacement of the actuator are compensated for in thatin each case a hollow-cylindrical restrictor gap, via which theamplifier chamber is linked to a liquid-filled low-pressure space, isprovided on the guide surfaces of the pistons, between the pistons andbetween the pistons and the inside wall of the valve housing. The volumedefined by the amplifier chamber, the restrictor gaps, and thelow-pressure space is sealed.

In the case of the lifting device known from German Patent ApplicationNo. DE 195 00 706 A1, above all the costly construction and the overalllength of the valve are disadvantageous. The relatively large volume andrelatively large cross-sectional area of the actuator also do not allowfor a particularly compact design. In addition, the large displacementvolumes result in a high cavitation tendency in the restrictor gaps.

SUMMARY OF THE INVENTION

The fuel injection valve according to the present invention has theadvantage that the lifting device is flexibly configured, and that thetemperature is easily compensated in addition to translating andreversing lift.

The seals configured as corrugated tubes are flexible, so that lineardeformations are compensated for.

In addition, the flexibility of the seals improves the dynamicperformance of the fuel injection valve, since the flexible corrugatedtubes prevent the valve-closure member from chattering on the valve-seatsurface and, as such, largely prevent the fuel injection valve fromopening again. The result is increased accuracy in the metering timesand metering amounts.

As a result of the partial accommodation of the valve needle in thecentral recess of the actuator, the tube-shaped actuator allows for aparticularly compact and light design of the fuel injection valve, atube-shaped valve needle sealed with respect to a nozzle body being atthe same time used for supplying fuel to the sealing seat.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows an axial section of an exemplary embodiment of a fuelinjection valve according to the present invention.

DETAILED DESCRIPTION

FIG. 1 shows an axial sectional view of an exemplary embodiment of afuel injection valve 1 according to the present invention. In thiscontext, fuel injection valve 1 is a fuel injection valve that openstowards the inside. Fuel injection valve 1 is particularly used todirectly inject fuel into the combustion chamber of amixture-compressing internal combustion engine having externallysupplied ignition.

Fuel injection valve 1 includes an actuator 2, which is composed ofdisk-shaped piezoelectric or magnetostrictive elements 3 and has atube-shaped design. Therefore, actuator 2 has a central recess 4, intowhich a valve needle 5 is inserted. Valve needle 5 has a tube-shapeddesign and is provided with a central recess 6, through which the fuelflows. The fuel is supplied via a connecting sleeve 8 into anipple-shaped extension 9 of valve needle 5.

A first front end 10 of actuator 2 abuts on an actuator cover plate 11.Actuator cover plate 11 and valve needle 5 are connected to one anotherby a first fuel seal 12, which is designed as a corrugated tube in theexemplary embodiment. First fuel seal 12 seals an actuator housing 13against the fuel, which is centrally supplied via connecting sleeve 8. Asecond fuel seal 14, which is also configured as a corrugated tube inthe exemplary embodiment, seals actuator housing 13 in the spraydirection. Second fuel seal 14 is welded to actuator housing 13 andvalve needle 5.

A translation device 15 is enclosed in actuator housing 13. Translationdevice 15 includes an actuator base plate 16, which abuts on a secondfront end 17 of actuator 2. A tube-shaped intermediate piece 18, whichis supported by a radial projection 19 on a first end 20 of acompression spring 21, is connected to actuator base plate 16 via awelded seam 26 b. A second end 22 of compression spring 21 is supportedon a support plate 23, which abuts on the inside on a shoulder ofactuator housing 13. Intermediate piece 18 and support plate 23 areconnected to one another by a first flexible seal 24.

Actuator base plate 16 and intermediate piece 18 reach behind a driver25, which has an L-shaped cross section and is fixedly connected via aweld seam 26 a to valve needle 5. On the one side, driver 25 isconnected, preferably via welding, by a second flexible seal 27 tosupport plate 23, and on the other side, by a third flexible seal 28 toradial projection 19 of intermediate piece 18. The three flexible seals24, 27, and 28 are configured in the exemplary embodiment as corrugatedtubes and enclose a pressure space 29 of translation device 15, which isfilled with a hydraulic medium. Compression spring 21 is enclosed inpressure space 29.

Valve needle 5 is connected in the spray direction to a valve-closuremember 30, which forms a sealing seat with a valve-seat surface 31. Thefuel is directed via transversely running channels 32 in valve needle 5into an intermediate space 34 located between valve-closure member 30and a nozzle body 33 and further to the sealing seat, where it isspray-discharged via at least one spray-discharge opening 36 formed in avalve-seat member 35.

Piezoelectric elements 3 of actuator 2 expand if an electrical voltageis applied to actuator 2. Since actuator 2 rests securely againstactuator housing 13 via actuator cover plate 11, actuator 2 can onlyexpand in the spray direction, thereby pressing actuator base plate 16including intermediate piece 18, which is connected thereto in afriction-locked manner, in the spray direction. Intermediate piece 18presses compression spring 21 further together, against the alreadyexisting prestress. As a result of intermediate piece 18 moving, thehydraulic medium sealed in pressure space 29 of translation device 15 isdisplaced, thereby moving driver 25 in the direction of the opening.Driver 25 has an operative connection to valve needle 5, which causesthe valve needle to also move in the direction of the opening.Valve-closure member 30 lifts off of valve-seat surface 31, and the fuelis sprayed through spray-discharge opening 36, which is formed invalve-seat member 35.

It is possible for translation device 15 to reverse the direction of theactuator stroke due to the fast actuating speed of actuator 2. In thiscase, the hydraulic medium behaves incompressibly. The hydraulic mediumbeing displaced results in a pulse transmission.

The present invention is not limited to the represented exemplaryembodiment, but is also possible in the case of a plurality of othertypes of construction of fuel injection valves 1, particularly in thecase of fuel injection valves 1 opening toward the outside.

What is claimed is:
 1. A fuel injection valve comprising: a valve-seatsurface; a valve-closure member interacting with the valve-seat surfaceto form a sealing seat; a valve needle; an intermediate piece; anactuator for actuating the valve-closure member via the valve needle andfor actuating the intermediate piece, the actuator being one ofpiezoelectric and magnetostrictive; a driver for actuating the valveneedle; a support plate; a first flexible seal connecting theintermediate piece to the support plate; a second flexible sealconnecting the support plate to the driver; and a third flexible sealconnecting the driver to the intermediate piece.
 2. The fuel injectionvalve according to claim 1, wherein the fuel injection valve is aninjection valve for a fuel injection system of an internal combustionengine.
 3. The fuel injection valve according to claim 1, wherein thefirst, second and third flexible seals, the intermediate piece, thedriver and the support plate form a hermetically sealed pressure spaceof a hydraulic translation device.
 4. The fuel injection valve accordingto claim 3, further comprising a compression spring situated in thepressure space, the pressure space being filled with a hydraulic medium.5. The fuel injection valve according to claim 4, wherein a first end ofthe compression spring is supported on a radial projection of theintermediate piece and a second end of the compression spring issupported on the support plate.
 6. The fuel injection valve according toclaim 5, wherein the third flexible seal is connected to the radialprojection of the intermediate piece.
 7. The fuel injection valveaccording to claim 1, wherein the driver is fixedly connected to thevalve needle by welding.
 8. The fuel injection valve according to claim1, wherein the first, second and third flexible seals are flexiblecorrugated tubes.
 9. The fuel injection valve according to claim 1,wherein the actuator and the valve needle are tube-shaped, and the valveneedle extends through the actuator.
 10. The fuel injection valveaccording to claim 9, wherein fuel is supplied through the valve needleto the sealing seat, and further comprising an actuator housing andfirst and second flexible fuel seals, and wherein, with respect to theactuator housing, the valve needle is sealed on an intake end by thefirst flexible fuel seal and on a spray end by the second flexible fuelseal.